Conventionally, there has been known a technology (for example, refer to Patent Literature 1) whereby two markers provided in right and left fenders of a vehicle is detected out of a photographed image of a vehicle periphery by an onboard camera, and an effective area in the photographed image is set so that respective markers may take specific positions set up in advance.
The inventors of the present application have found out the following. With a technology described in Patent Literature 1, since a deviation of an installation position of an onboard camera is detected using a marker whose installation position is known, the technology cannot necessarily apply to any onboard camera due to a disposition restriction of the marker.